A while back I was ripping some capacitors out of a board in hopes that they would come out all right, since I didn't have any kind of device capable of soldering at that time.

I actually managed to get some capacitors out undamaged, but about half of them were scrap.

So I was thinking one day, and I took apart one of the larger scrap capacitors, stuck a transistor into the rubber stopper with the leads pointing out, and put it back together.

Then I thought, "Hey, now I've got a low-noise transistor!"

Of course, I knew that stuffing a transistor in a metal case would not make it any less noisier, but I was very board at the time and I was trying desperately to occupy myself.

But this does perk my interest a bit. For large capacitors, someone careful enough could point-to-point solder a simple transistor circuit just small enough to fit in the capacitor case. Even some capacitors are large enough to house two TO-92 transistors, which you could make into a darlington package or something. You could construct a frequency filter and stuff it in one so that the coil would not pick up as much EMI. You could make a low-power dummy antenna by wiring up a bunch of resistors, filling the capacitor casing with oil, and sticking it in. You might also be able to help heat problems by using oil like that. If you were using a relay with high enough voltages to spark, you could put that in it and ground the case so that it wouldn't emit interference like a spark-gap.

Naturally, the larger the capacitor the better, so that you can stuff more in.